question

It's difficult to list out all of the places a breathe may be required. I can try and give you some general places where you may need one.

Triggers/events of 3D objects:

If you're listening to a trigger or other event from a 3D object and then manipulating something in 3D you may need a breath. For example, if you listen to the On Entry of a Queue and then in your process flow you want to move the entering item from the queue to another object, you'll need a breath. This is because the activities that are being executed in process flow are happening inside of the On Entry on the Queue. The Queue's logic expects that the flowitem will still be there once the entry trigger is fired. If the flowitem has moved on to another object, it may through exceptions. This can be true of processors, racks etc.

If you're listening to one of these triggers/events and you manipulate unrelated 3D objects, then a breathe will not likely be necessary. For example, listening to the On Entry and then creating a flowitem in completely separate queue.

After a Push or Pull From List:

Not always, but there may be times that you need a breathe immediately after pushing or pulling from a list. Say your list is full flowitems that are ready to be processed. If they are being pushed onto the list when they enter a queue, then the Pull From List may fire during the On Entry event, similar to the above case.

You'll find that most often the breathes are needed when working with 3D objects, however, similar issues to those described above can also occur within process flow activities. If you find that your model is not behaving as expected, or exceptions are being thrown after adding in a set of activities, you may try putting a breathe activity in there. If the problem was not resolved, then the issue is likely something else.

If you have questions about a specific set of logic, feel free to post them here and we can try and help walk you through what's going on.